Modulation of endotoxin-induced endothelial function by calcium/calmodulin-dependent protein kinase

Abstract

Endothelial cells facilitate sepsis-induced neutrophil adherence through the production of adhesion molecules and proinflammatory cytokines. The production of these factors requires coordinated intracellular inflammatory signaling. Recently, patients prone to sepsis-induced complications have been shown to have derangements in intracellular calcium and potentially calcium/calmodulin-dependent protein kinase (CaMK) activity, but the impact of these impairments is unknown. Human umbilical vein endothelial vein endothelial cells (HUVECs) were exposed to lipopolysaccharide (LPS) for various periods of time. Select HUVECs were pretreated with an inhibitor of CaMK II, KN62. Total cellular and nuclear proteins were extracted and analyzed for various components of the Toll-mediated signal cascade. Neutrophil adhesion was assayed fluorometrically using calcein-labeled neutrophils on treated HUVECs. LPS stimulation led to mitogen-activated protein kinase activation and translocation of activator protein-1 (AP-1) and nuclear factor (NF)-kappaB. CaMK blockade inhibited LPS induced ERK 1/2 and JNK but enhanced p38 activity. This selective MAPK inhibition was associated with a reduction in AP-1 activity, with no affect on NF-kappaB activity. Associated with this altered cell signaling was increased ICAM-1 production and enhanced neutrophil adhesion. Altered CaMK activity resulted in dysregulated mitogen-activated protein kinase signaling, demonstrated by reduced ERK 1/2 and JNK activity but enhanced p38 activity. This altered signaling is associated with reduced AP-1 activation and unaffected NF-kappaB activation. Neutrophil adhesion, however, is enhanced presumably through increased ICAM-1 production. Therefore, CaMK inhibition of endothelial cells, characteristic of sustained increases in intracellular calcium, appears to result in a dysregulated proadhesive phenotype.